I recently bought a 1989 Gibson Country Gentleman guitar that was modified with taller pickup mounting rings. The mounting ring for the bridge pickup is about a half inch tall which positions the top of the pickguard almost even with the strings. I want to return this guitar back to the stock configuration. I have two questions - First, what are the heights of the pickup mounting rings that came stock from the factory? Second, where should I buy them and is there anything special I need to ask for?

They are just stock black Gibson humbucker mounting rings, measure the height of yours as fitted, then ask in any music store for some at whatever half the height of yours are. Plenty of adjustment latitude, so exact height is not too crucial. Can't get to my CG to measure the stock ones on that, currently.